1. Field of the Invention
The present invention relates to an acousto-optical space-switching matrix. In particular the present invention relates to an optical spatial switching matrix comprising N input ports and M output ports, in which it is possible to switch an optical beam from any of the input ports to any of the output ports.
2. Description of the Related Art
Acousto-optical based switches have been proposed in the past.
U.S. Pat. No. 6,016,216 describes a polarization independent acousto-optic tunable filter (PIAOTF) used for multi-wavelength switching and routing in wavelength division multiplexing (WDM) networks. In the PIAOTF an incident unpolarized light beam is divided to propagate and to be diffracted along two polarization division branches. By using polarization converters and equal optical paths for the two polarization division channels, a PIAOTF is created which minimizes polarization dependent loss and polarization mode dispersion. Furthermore, a preferred embodiment of the AOTF using an elongated acousto-optic interaction medium is described that provides the additional advantages of narrow bandwidth, lower drive power and easier alignment.
U.S. Pat. No. 5,909,304 proposes an acousto-optic tunable filter based on an isotropic acousto-optic diffraction medium excited with an acoustic wave generated from a phased array transducer. Said acoustic-wave causes a diffraction of an incident light into said acousto-optic diffraction medium in a way to obtain a frequency of the diffracted light, which is narrower than the optical frequencies of said incident light.
U.S. Pat. No. 5,852,688 describes a method for optical energy transfer and energy guidance using an electric field to control energy propagation using a class of poled structures in solid material. The poled structures, which may form gratings in thin film or bulk configurations, may be combined with waveguide structures. Electric fields are applied to the poled structures to control routing of optical energy. Techniques include frequency-selective switchable and adjustable-tunable reflection, splitting, directional coupling, frequency-tunable switching and efficient beam combining, as well as polarized beam combining. Adjustable tunability is obtained by a poled structure, which produces a spatial gradient in a variable index of refraction along an axis in the presence of a variable electric field. In one embodiment, the patent describes a method of switching a grating which consists of a poled material with an alternating domain structure of specific period. When an electric field is applied across the periodic structure, a Bragg grating is formed by the electro-optic effect, reflecting optical radiation with a certain bandwidth around a center wavelength. The grating may be used by itself, or in combination with other gratings to form integrated structures in a ferroelectric crystal. Specifically of interest is a method of using an integrated structure in which one or more optical waveguides interact with one or more periodic structures to form a wavelength selective integrated optical switch.
U.S. Pat. No. 5,457,556 describes an optical cross-connect system in which incoming and outgoing fiber optic trunks carrying WTDM signals are terminated to first inlet ports and first outlet ports of an optical space switch. A wavelength division demultiplexer is connected to a second outlet port of the optical space switch and a wavelength division multiplexer is connected to a second inlet port of the optical space switch. A wavelength-divided space switch has first inlet ports connected to the outputs of the wavelength division demultiplexer and first outlet ports connected to the inputs of the wavelength division multiplexer. A time division demultiplexer is connected to a second outlet port of the wavelength-divided space switch and a time division multiplexer is connected to a second inlet port of the wavelength-divided space switch. The outputs of the time division demultiplexer are connected to first inlet ports of a time switch and the inputs of the time division multiplexer are connected to first outlet ports of the time switch. The time switch has second inlet ports and second outlet ports connected to a switched network
U.S. Pat. No. 4,995,693 proposes an array of acousto-optic Bragg cells to couple one of a plurality of input light sources, or channels, to one out of a plurality of output terminals, or channels. By choice of the radio frequency tunable control, any of the inputs can be coupled to any of the outputs, by means of scan lenses.